Spark plug construction



Patented July 25, 1950 l UNITED STATES PATENT OFFICE SPARK PLUGCONSTRUCTION Chester Cipriani and Carl J. Eaton, Toledo, OhioApplication July 9, 1945, Serial No. 603,774

4 Claims.

This invention relates to spark plugs, more particularly to theelectrodes thereof, and to an eilicient cooperating temperaturedistribution in the spark plugs.

In internal combustion engine ignition systems it has long beendesirable to provide a selfc-leaning spark plug which would not fouleven though the engine was operating under the widest possible, mostexacting conditions. Self-cleaning features of a spark plug have beensought by attempting to control the heat range of the plug whereby thetemperature conditions in the parts of the plug exposed to burning gasesin the combustion chamber of the engine were such that formation anddeposition of carbon and other residues were retarded or burned away asrapidly as deposited. It has been attempted to maintain the temperatureof the ring tip of the insulator body within a range where the self-cleaning process would be continuous or at least sufiicientlyintermittent to maintain the plug in efcient firing condition. Often theselected heat range resulted in the plug remaining too cold when theengine was operated under idling conditions and fouling resulted, and ifthe heat range maintained resulted in providing a self-cleaning plug atidling speeds, the resultant hotter plug would break down at high speed,full load conditions. Furthermore, when plugs of this type were used intwo-cycle engines, this condition was materially aggravated and resultswere very unsatisfactory.

In two cycle engines, a cold plug would quickly foul at idling, while ahot plug, while not so fouling in the same sense, would be destroyed ina very short time under high speed, full load operating conditions.

The present invention results in the production of a spark plug which isinherently self-cleaning at the spark gap and is not dependent upontemperature conditions for the cleaning action to be eilicient. The heatrange of a plug utilizing the Y present invention is not a particularlymaterial cleaning. A series intensifier gap integral with the plug isprovided in coacting combination with 65 the annular gap to control thebreakdown voltage at the gap. The series gap is preferably sealed fromthe atmosphere to insure uniform breakdown voltage, despite variationsin ambient atmospheric conditions arising from pressure and/ or relativehumidity.

Itis, therefore, a principal object of this invention to provide a sparkplug which is self-cleaning under all conditions in the firing chamberof an internal combustion engine and is particularly independent oftemperature conditions in its selfcleaning operation.

It is a further object of this invention to provide a spark plugsatisfactorily operable with heat ranges which are encountered in allautomotive engines.

It is a further object of this invention to provide a spark plug havingan annular spark gap in series with an intensifier gap, which annulargap is self-cleansing and will not foul under widely varying conditionsin the combustion chamber of an internal combustion engine.

It is still a further object of this invention to provide aself-cleaning spark plug which is suitable for use in two-cycle engines.

Still an additional object of the invention is to provide an economicalspark intensifier construction of constant characteristics undervariable operating conditions and which is readily incorporated withinthe plug as a component of an electrode.

Other objects and advantages of this invention relating to thearrangement, operation and f unction of the related elements of thestructure, to various details of construction, to combinations of partsand to economies of manufacture, will be apparent to those skilled inthe art upon consideration of the following description and appendedclaims, reference being had to the accompanying drawings forming a partof this specification wherein like reference characters designatecorresponding parts in the several views.

Referring to the drawings:

Fig. 1 is a longitudinal section through a spark plug for an internalcombustion engine, the plug embodying features of the invention herein;

Fig. 2 is a longitudinal section through a spark plug of the shieldedtype and embodying additional features of the invention;

Fig. 3 is a view, similar to Fig. 2, showing a modied form of the sparkintensifier and of the heat distribution `features;

Fig. 4 ls a longitudinal section, on an enlarged scale, through thespark intensifier element disclosed in the structure of Fig. 3; and

Fig. 5 is a distributed view of the parts forming the assembly of acenter electrode employed in a construction of a spark plug of theinvention herein.

Referring to Fig. l, the spark plug disclosed comprises a base or shellmember having threaded extension I2 1for mounting the plug on an enginewith the extension extending into the firing chamber thereof (notshown). This shell is provided with external polygonal portion I4 bywhich the plug may be securely mounted in operative position, andinternal chamber I6 having ledge I8 as a seat for sealing gasket 20,upon which enlarged portion 22 of insulator 24 is mounted and held ingas-tight relationship as by spinning the upper edge 26 of the shellover compression ring 28 which is forced against the upper perimeter ofthe enlarged portion of the insulator.

The ceramic insulator has extension 30 through the threaded portion I2extending into a nring chamber. Ground electrode 32, in the form of anickel or suitable alloy ring, surrounds the extension and is fixed tothe portion I2 by brazing or welding, employing, for example, a silversolder. The lower terminus of the extension is juxtaposed to and extendsbeyond the electrode 32 for a predetermined distance whereby an annularportion of the insulator surface is exposed.

The spark plug is provided with a sectional center or firing electrode,mounted axially of the insulator, which electrode comprises a ring plate36 having a peened or other suitable connection 38 with stem 4I|extending upwardlyv as a core into the insulator 24. The ring 36 isiixedly held against the insulator terminus 30 in concentric relation asto the ground electrode 32, thereby forming an annular spark gap 42,across which there may be an ionized electronic flow in the sparkingoperation. This ow may be of a 0 sweeping or scrubbng nature across theexposed surface of the insulator which maintains this region free fromany deleterious accumulations and hence resulting in a self -cleaningplug. The

plate 60, against which the expanded head or a. tubular eyelet or rivettype conductor 62 may be placed in electrical communication therewith.This member 62 extends outwardly toward upper portion. of the insulatorto there engage a terminal 84, which is mounted on the insulator andwhich terminal is adapted to be engaged by a suitable connector withlead 66 extending from a high tension electrical energy source 68, suchas an ignition circuit for an internal combustion engine.

It will be seen energy flow in the circuit is from the source 68,through lead 66, terminal 64, tubular conductor 62, to the plate andthen jumps or by-passes the ceramic rod element to.

plate 56. There is thus formed a controlled intensiiier gap 10 in serieswith the stem portions 44, 40, the annular ring 36, the spark gap 42 toground. The intensifier gap 10 is of relatively higher voltage breakdownthan the ignition spark gap 42. By the use of one or more plugs incooperation with a firing chamber of an internal combustion engine, acontinued desirable igniter source is provided for fuel. The member 62may also be surrounded by a sealing pack 52 on washer or gasket 50,resting against the expanded head, which pack fills and seals the duct54 about this portion of the electrode. construction so described, heatfrom the region of the gap 42 is readily radiated by the insulatorportion 22, through the shell and dissipated into the atmosphere ortransmitted to the engine block and with the washback 48 and theclearance 12 between the extensions I2 and 30 fractures are reduced to aminimum by elimination u of any localized heating.

The invention may be satisfactorily incorporated in plugs not onlyenjoying the full selfcleaning advantages but adapted, through bodydesign, to meet the problems encountered in various temperature rangesso a plug of maximum cold range operation results.

For example, referring to Fig. 2, showing a shielded type of spark plug,the sectional elecstem l0 terminates in a reduced diameter por- 45trede. including the spark gap denning elements,

tion 44 within the body of the ceramic insulator. As an assembling andsealing means for this electrode and insulator, a suitable cement 46 maysurround the upper portion of the stem 40, leaving a clearance orwashback 48 within the plug w body between the ring 36 and the cement,which clearance may be of a predetermined length and insures againstfracture of the firing tip and along the insulator extension 30, due tothe wide changes in temperature encountered in this u region.

A washer 50 of asbestos or other suitable material may be placed aroundthe stem portion 44 adjacent the terminus of the major diameter stemportion 40, and a filler placed about the .o

remainder of the portion 44 in the form of a powder-pack 52 of talc,ceramic powder, or the like.

Resting against the free end of the stem portion 44, within the axialbore 54 through the inu and of a diameter about .010" less than thediameter of the bore or duct 54. These dimensions are quoted as atypical example but, of course, are subject to considerable variation ina range of spark plug designs. Against the rod end, re-

may be mounted in insulator 14 having -portion 16 downward-ly taperingand terminating in the spark gap 42, said portion upwardly terminatingin shoulder 18, and from which there extends tapered portion 80.Surrounding a fraction of the surface of the portion 16 is a high heatconductive metallic sheath or gasket 82 which may be of copper, silver,or the like. This gasket rests on inner face 84 of shell 86, the extentof. the face 84 being complementary to the taper of t the insulatorportion 16. The shell 86 is provided with lower internal seat 88, inwhich the ground electrode 32 may be fixed.

The shell 86 is also provided with an upwardly extending chamber z90.

Resting upon the shoulder 18 within Athe chamber is a compensator spring92, abutted by spring rest -84 which, by the threaded action betweenshielding sleeve 98 and the shell 86, the spring rest is forced againstthe Vcompensator spring, thereby assembling these parts in sealingrelation.

Within the shielding sleeve 86 and concentric therewith is insulatortube 88, positioned by two retainers |00, |02, the tube being held inposition by a spinning thereover of a portion of the up' ward terminusof the shielding sleeve-96. The tube retainer |00 is held against theupper end of the tube 98 and the retainer |02 may be bemote from theplate 56, there is disposed a second 15 tween the upper surface of thespring rest 94 In the and the lower edge of the insulating tube 98 withretainer extensions between the tube and shielding sleeve. Theelectrical energy may be conducted to the sectional electrode by placingplate |04 on the upper terminus of the conductor 82, against which hightension lead |08 may be positioned by means'of iitting |08 in insulationbushing ||0, held in position within the insulating tube 98 by means ofinsulator grommet H2, collar H4, and gland nut ||6 in threadedconnection with the shielding sleeve 98. Spring ||1 may be insertedbetween the plate |04 and bushing ||0 to improve the electric contactsand maintains the related parts in assembled position. This high tensioncable |06, together with the ignition system 88, may be entirelyshielded, as indicated by the dotted lines in Fig. 2, thereby defeatingany transmissions which may interfere with radio reception in theneighborhood employing this invention.

The eifect of this shielding is to also increase the capacitance ofignition system with the resulting benefits.

It is to be noted, by such an insulator mounting, heat is rapidlytransferred from the portion 16 through the gasket 82 into the shell 88to be dissipated thereby. Y

Referring to Fig. 3l, the center electrode insulator embodies acylindrical central portion ||8 with upper and lower shoulders |20, |22,which portion I8 is mounted in complementary chamber |24 of the shell 86ywith the shoulder |22 on sealing gasket |26 between it and the shell,while the shoulder |20 cooperates with a superstructure, similar to thatshown in Fig. 2. Here again, a modified structure is disclosed forsatisfactory operation within a predetermined heat range whereby allheat from the spark gap 42 is dissipated through the cylindrical portion||8 without any localizing.

While a satisfactory intensifier gap is formed by placing a dielectricseparator 58 of calculated dimensions between plates 56, 60, improvedresults for some conditions may be had by using another form of spacer,such a dielectric tube |28 of glass or the like, having electrodes |30,|32, extending into bore |34 through the tube, the electrodes beingprovided with terminal plates |38, |38 which may Ibe placed inelectrical contact relation in series with the center electrode. Theelectrodes |30, |32 are hermetically sealed within the body |28, and thespace between their termini within the bore |34 may be evacuated orillled with an inert gas. By the use of this latter spacing element, aconstant pressure in the intensiiler gap is maintained, regardless ofambient pressures or relative humidity.

In a spark plug of the more common dimensions, this sealed series gap,especially adapted for use in a shielded plug, has an lapproximateoverall length of with a gap length approximating .160-.150 to givebreakdown of 6,000-9,000 peak volts, the voltage toremain within theselimits when the gap is subjected to 29" Hg vacuum and 650 degrees Fahr.temperature for 8 hours. Again, these ilgures are given to indicate butone satisfactory range well within limits allowable in either directiontherefrom.

It is to be understood that the above detailed the invention is capableof being practiced and carried out in various ways without departingfrom the spirit of the invention. The language used in the specificationrelating to the operation and function of the elements of the inventionis employed for purposes of description and not of limitation, and. itisnot intended to limit the scope of the following claims beyond therequirements of the prior art.

What is claimed and it is desired to secure by United States LettersPatent:

l. In combination with a source of high tension electrical energy, aspark plug having a spark gap defined by two electrodes one of which isgrounded, an insulating body of ceramic material insulating the otherelectrode from said grounded electrode, said insulating body beingexposed to the electric spark between the two electrodes in the sparkgap and subject to the action of ionization of the electric spark, andan intensifier gap having a break-down voltage from 6 to 9 thousand peakvolts, relatively higher than the break-down voltage of the spark gap,said intensifier gap being positioned in the spark plug adjacent thespark gap and connected in series with a source of electrical energy andthe spark gap.

2. The combination set forth in claim l further characterized by havingthe intensifier gap positioned in a hermetically sealed chamber.

3. The combination set forth in claim 1 further characterized by havingthe intensiiier gap positioned in a sealed chamber containing an inertgas.

4. In combination with a source of high tension electrical energy, aspark plug having a spark gap defined by two concentric electrodes, oneof which is grounded, an insulating body of ceramic material insulatingthe other electrode, said insulating body being exposed to the electricspark between the electrodes and subject to the action of ionization ofthe electric spark, and an intensiiier gap of relatively higherbreak-down voltage than the spark gap and positioned adjacent thereto inseries with the source of electrical energy and the spark gap, saidelements of the spark plug being arranged for maximum heat conductivitywhereby a cold rating is acquired for the plug in its intended use.

CHESTER CIPRIANI. CARL J. EATON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATESv PATENTS Number Namev Date 754,666 Miller Mar. 15, 19041,233,630 White July 17, 1917 1,461,405 Solomon July 10, 1923 1,488,526Butler Apr. 1, 1924 1,502,682 Reed July 29, 1924 1,518,248 Broluska etal Dec. 9, 1924 1,537,903 Von Lepel May 12, 1925 1,613,494 Von LepelJan. 4, 1927 1,962,669 Parkin June 12, 1934 2,142,383 Smith Jan. 3, 19392,376,362 Kasarjian May 22, 1945 .FOREIGN PATENTS Number Country Date555,865 France July 7. 1923 581,361 France Nov. 2'?. 1924

